This invention relates generally to transport refrigeration systems and, more particularly, to the cooling of an engine driven generator therefor.
Generally, transport refrigeration systems such as those used on truck trailers, have employed belt driven and/or mechanically linked, shaft driven compressor units and/or belt driven, or otherwise mechanically linked, fan powering systems. That is, the unit engine, such as a diesel engine, is mechanically connected to drive both the compressor unit(s) and the unit refrigeration systems fans and other components.
A significant improvement to such an arrangement was a so called “all electric” transport refrigeration system as described in U.S. Pat. No. 6,223,546, assigned to the assignee of the present invention. In such a unit, a generator is mechanically connected to the system engine and is used to generate the electrical power needed to drive the compressor and the various refrigeration system fans and other components.
Heretofore, such an engine driven generator has been cooled by a fan disposed on one end thereof and adapted to circulate air over the stator and armature components for the cooling thereof. A significant cooling effect is also achieved by moving air over the generator by the condenser fans.
The applicants have recognized that a significant volume of air at a substantially high pressure is required to provide the necessary cooling, particularly for obtaining sufficient circulation through the small openings in the rotor to obtain the required cooling.
Another problem that has been recognized in such air cooled systems is the occurrence of generator shorting that is caused by outside contamination. That is, the transportation environment is a harsh environment and, as the outside air is circulated through the generator, there is a tendency for contaminants to enter the unit and cause an electrical shorting of the windings. This results in damage to the components and to expenses due to down time.
What is needed is an improved method and apparatus for cooling the generator of an electrically powered transport refrigeration unit. Of particular interest is a reduction of size and weight.